To make a denture easily detachable in dental implanting, a method of fixing a soft-magnetic keeper to an implant body embedded in the jawbone, and causing a magnet-containing denture attachment to be magnetically attracted to the keeper has recently become widely used.
U.S. Pat. No. 6,709,270 discloses a magnet-containing denture attachment magnetically attached to a keeper made of a soft-magnetic material and threadably engaging an implant body. The keeper comprises a frustoconical portion, and a ring portion extending from an upper peripheral of the frustoconical portion and provided with an annular groove to have a lower end portion having a gradually reducing thickness. The implant body comprises a conical recess complementary to the frustoconical portion of the keeper. When the keeper is screwed into the implant body, the lower end portion of the ring portion abutting the implant body is elastically deformed, generating tension by which the keeper is prevented from slackening. However, because there is a small contact area between the lower end portion of the ring portion and the implant body, plastic deformation occurs in the lower end portion of the ring portion by a long period of use, resulting in decreased tension and thus slackening the keeper.
In the implanting of front teeth to the upper jaw, etc., an abutment with an angled head is used to make a slanting denture. For instance, EP 0323421 A discloses a dental implant, in which an angled spacer is attached to an implant body embedded in the jawbone, and a dental bridge is fixed to a spacer head with a bolt. However, because the dental bridge to be fixed to the angled spacer with a screw does not have a female thread, the dental bridge is not firmly fastened to the angled spacer, resulting in slackening by a long period of use.